The invention described herein may be manufactured and used by or for the government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
1. Field of the Invention
The present invention relates to rocket motors. More particularly, the rocket motor of the present invention includes an ordnance venting system to reduce the danger of explosion for heat induced over-pressurization. Most particularly, the ordnance venting system has a thermoplastic warhead adapter that melts prior to rocket cook-off to prevent cook-off.
2. Brief Description of the Related Art
The MK 66 Rocket Motor is a 2.75-inch diameter weapon system used by the United States armed services that is stored and operated from land and sea. Stringent cook off requirements improve safety to personnel and property in the event that an ordnance system is initiated by excessive heat.
Several patents disclose munition venting systems. U.S. Pat. No. 3,927,791 (Hershberger) discloses a fusible plug assembly of a bismuth alloy that melts at approximately 210xc2x0 F. to permit venting. U.S. Pat. No. 4,557,198 (Hickey) discloses a venting aperture with two retaining means and a shear pin configuration. U.S. Pat. No. 4,991,513 (Malamas, et al.) discloses a plurality of vent holes in the nose section that are open when coincident with vent holes in a collar. In storage, the vent holes are left open with the placement of a safety pin, which is removed immediately prior to loading. U.S. Pat. No. 5,035,180 (Purcell, et al. ""180) discloses a venting system having a metal patch attached to the casing that shears from the casing when heated. U.S. Pat. No. 5,035,182 (Purcell, et al. ""182) discloses a vent system having a bi-metallic patch attached to the casing that deforms with heating, which then separates from the casing. U.S. Pat. No. 5,155,298 (Koontz) discloses a solder plug that melts which retracts a snap ring and confines the explosive material by an adapter plate; with increase in warhead internal pressure, radial set screws shear freeing the adapter plate which release and vent the pressure within the warhead case. U.S. Pat. No. 5,311,820 (Ellingsen) discloses a melting fusible material that allows a free-loaded spring retainer to push the melted or liquid fusible material out of a set screw hole, causing the nozzle to separate from the case at the interface. U.S. Pat. No. 5,337,672 (Boissiere, et al.) discloses a set of locking screws that secures a casing to a plug, with the locking screws designed to shear at a given pressure. U.S. Pat. No. 5,398,498 (Mort, et al.) discloses a fusible helical joint member made of a metallic material having a low melting point that melts when heated, allowing an adapter ring to disconnect the warhead from the rocket motor. U.S. Pat. No. 5,735,114 (Ellingsen) discloses a bimetallic retaining ring that releases the engagement between two or more sections of a rocket motor when contacted by an external heat source. U.S. Pat. No. 5,939,662 (Bootes, et al.) discloses explosive blowout ports that allow heat to enter the fuse body and slowly burn booster charged explosives allowing the explosives to burn off quickly without exploding.
Although the identified patents disclose several types of missile venting devices, none of the patents disclose a non-complex reliable pressure released plug that improves the MK 66 rocket motor""s response to insensitive munition (IM) threats, such as fast cook-off, slow cook-off, bullet impact, fragment impact and sympathetic detonation. The present invention addresses these and other needs.
The present invention includes an ordnance venting system to reduce the danger of explosion from heat induced over-pressurization comprising an ordnance device having a casing with a vent opening formed therein, a dome plug fitted into the formed vent opening, wherein the dome plug completely covers the formed vent opening and an adapter fitted over the dome plug on the outside of the casing, the adapter connected sufficiently to the casing to retain the dome plug against the formed vent opening, wherein the adapter melts at high temperatures.
The present invention also includes a method of venting an ordnance device comprising the steps of providing an ordnance venting system to reduce the danger of explosion from heat induced over-pressurization, comprising an ordnance device having a casing with a vent opening formed therein, a dome plug fitted into the formed vent opening, wherein the dome plug has sufficient width to cover the formed vent opening and an adapter fitted over the dome plug on the outside of the casing, the adapter connected sufficiently to the casing to retain the dome plug against the formed vent opening, wherein the adapter melts at high temperatures, and melting the adapter at a predetermined temperature, wherein pressure within the casing ejects the dome plug from covering the formed vent opening, release the pressure from within the casing.
The present invention further includes a vented ordnance device product produced from the method comprising the steps of providing an ordnance venting system to reduce the danger of explosion from heat induced over-pressurization, comprising an ordnance device having a casing with a vent opening formed therein, a dome plug fitted into the formed vent opening, wherein the dome plug has sufficient width to cover the formed vent opening and an adapter fitted over the dome plug on the outside of the casing, the adapter connected sufficiently to the casing to retain the dome plug against the formed vent opening, wherein the adapter melts at high temperatures, and melting the adapter at a predetermined temperature, wherein pressure within the casing ejects the dome plug from covering the formed vent opening, release the pressure from within the casing, and the vented ordnance device is sufficiently vented to prevent cook-off.